Really good alternative to alcohol markers, sort of like crayon, cleanup with wet towel. Awesome all around, dirt cheap... They also got blackboard kits.
http://www.rikagaku.co.jp/items/kitpaslist1.php
Plus the company employ mostly handicaped people (I mean with real disabilities, not politicians or run of the mill japanese imbeciles).
Non toxic... and yes, you can poop rainbows...